Adaptive communication interface

ABSTRACT

Embodiments of the invention include a communication interface and protocol for allowing communication between devices, circuits, integrated circuits and similar electronic components having different communication capacities or clock domains. The interface supports communication between any components having any difference in capacity and over any distance. The interface utilizes request and acknowledge phases and signals and an initiator-target relationship between components that allow each side to throttle the communication rate to an accepted level for each component or achieve a desired bit error rate.

CLAIM TO PRIORITY

This is a divisional application of co-pending U.S. patent applicationSer. No. 10/976,572, filed Oct. 29, 2004, and published as U.S. PatentPublication No. 2006/0117231.

BACKGROUND Field of the Invention

The invention relates to communication interfaces and protocols.Specifically, embodiments of the invention relate to a method andapparatus for communicating between devices having differentcommunication capacities, operating speeds and devices operating indifferent clock domains.

BACKGROUND

Communication between components of a computer system across the printedcircuit board (PCB) of a main board utilizes either parallelcommunication buses or serial communication buses. Conventional highspeed parallel communication buses require very tight controls on theamount of skew or distortion on the communication lines. These tightrequirements result in a difficult process for determining a properlayout of the communication lines on a PCB. The communication lines in aparallel bus must be balanced, have matching impedances and similarphysical characteristics. These conventional high speed parallel busesdo not support communication between devices with differingcommunication rates, capacities or speeds. Conventional high speedparallel buses make overall PCB layout and design more difficult andtime consuming for main board manufacturers.

Conventional high speed serial communication buses avoid some of theproblems of high speed parallel buses but require more complex digitalsignal processing by the components communicating over the high speedserial bus. High speed serial buses require the communicating componentsto determine clock recovery, undergo pre-emphasis of the serial line,perform synchronization and similar digital signal processingcalculations. Components in a computer system that utilize high speedserial buses must devote significant resources and integrated circuitspace to perform the requisite digital signal processing functions. Highspeed serial buses are also unable to support communication betweendevices having different communication capabilities. Neither high speedparallel nor serial buses support communication between componentsmanufactured according to the most current communication and data ratestandards and legacy components. This requires manufacturers to abandonthe use of legacy components when a new communication standard isadopted in an industry.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example and notby way of limitation in the figures of the accompanying drawings inwhich like references indicate similar elements. It should be noted thatreferences to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

FIG. 1 is a diagram of one embodiment of an initiator component and atarget component.

FIG. 2 is a flowchart of one embodiment of a process for initiating awrite operation.

FIG. 2B is a flowchart of one embodiment of a process for handling awrite operation at a target device.

FIG. 3 is an example timing diagram of a set of signals between aninitiator component and target component during a write operation.

FIG. 4 is a diagram of one embodiment of an initiator component andtarget component.

FIG. 5A is a flowchart of one embodiment of a process for initiating aread operation.

FIG. 5B is a flowchart of one embodiment of a process for handling aread request at a target component.

FIG. 6 is an example timing diagram of signals between an initiatorcomponent and target component during a read operation.

FIG. 7 is an example timing diagram of a set of signals between aninitiator component and target component during a read and writeoperation.

FIG. 8A is a diagram of one embodiment of initiator component and targetcomponent that operate in separate clock domains.

FIG. 8B is a diagram of one embodiment of an initiator component andtarget component operating in different clock domains.

FIG. 9A is a diagram of one embodiment of an initiator component andtarget component that utilize a training sequence.

FIG. 9B is a diagram of one embodiment of an initiator component andtarget component that use a training sequence.

FIG. 10 is a diagram of one embodiment of a computer system utilizinginitiator components and target components to communicate between thedevices on the main board.

FIG. 11 is a diagram of one embodiment of a use of initiator componentsand target components in network devices.

DETAILED DESCRIPTION

FIG. 1 is a diagram of one embodiment of a communication medium governedby an initiator component and target component interface in the contextof a write operation. The communication medium may be any type ofcommunication medium including parallel or serial lines in a bus on aprinted circuit board or in an integrated circuit, optical or coaxialcabling between network devices or any other type of communicationmedium. The communication medium may have any capacity or speed. In oneembodiment, the communication medium may be a data bus 125 or similarset of communication lines.

In one embodiment, this communication medium may be governed by aninitiator component 101 and a target component 111 interface. Theinitiator component 101 may be situated in or in communication with adevice that communicates over the communication medium. Similarly, thetarget component 111 may be situated in or in communication with adevice to assist in managing communication over the communicationmedium. For example, the initiator-target interface may be used togovern communication between a central processing unit and a chipset ona main board. The initiator component 101 may be situated in the centralprocessing unit and the target component 111 may be situated in thechipset. The devices associated with the initiator component 101 andtarget component 111 may have different operating speeds, clock domains,communication transfer rates or other dissimilarities in communicationcapabilities.

In one embodiment, in addition to the standard communication lines fortransmitting and receiving data, the initiator-target componentinterface may have a dedicated request line 127 and dedicatedacknowledgment line 129. These lines may be utilized by the interface tomanage the flow of data over the standard communication lines. Theinitiator-target component interface may minimize the number ofauxiliary communication lines required to manage communication over acommunication medium. This also minimizes the needed number of pins onan integrated circuit or number of lines in a communication medium. Incontrast, other communication interfaces or protocols require additionaldedicated communication lines and pins to send a clock signal and otherflow control signals. The initiator-target component interface mayutilize two control signals in addition to the data lines requiredbetween the communicating devices. The standard data lines maycommunicate any type of data including command signals, storage data,program data, instruction data and similar data. The initiator-targetcomponent interface saves power and integrated circuit or main boardspace over traditional communication interfaces.

In one embodiment, an initiator-target component interface may beutilized to manage communication over a communication medium between anytwo or more devices at any level of communication irrespective ofrelative communication capacities of the devices. The interface may beused within integrated circuits, chip to chip, device to device, innetwork communications and similar communication scenarios. Theinterface allows the devices utilizing the interface to throttle thecommunication speed over the communication medium to maximize throughputbetween the components without exceeding a desired bit error rate andwithin the communication capabilities of each device. In one embodiment,the initiator-target component interface may be capable of executingwrite operations from the initiator component to the target componentand read operations from the target component to the initiatorcomponent. The initiator component may signal the initiation of a readoperation before data is sent by the target component. FIGS. 1-3 relateto a write operation. FIGS. 4-6 relate to a read operation.

In one embodiment, the interface also may be utilized over any distancefrom short distances within integrated circuits to long distancesbetween network devices. In addition to allowing the communicatingdevices to throttle the speed of communication the interface alsoadjusts the communication rate to account for skew and distortion ofsignals on the communication medium such as signal noise and reflection.The interface may be ‘tuned’ for communication over a specific mediumand for specific devices or may be trained to dynamically adjust tochanging conditions, communication mediums and devices. The interfacemay be utilized in conjunction with asynchronous devices and synchronousdevices. The embodiment of the interface initially discussed in relationto FIGS. 1-7 is an asynchronous embodiment. A synchronous embodiment isdiscussed in relation to FIGS. 8A and 8B.

In one embodiment, the initiator component 101 may include or be incommunication with a storage device 103. The storage device 103 may beany type of storage device including a set of buffers, set of registers,random access memory device, fixed storage device, or similar storagemedium. The target component 111 may also include or be in communicationwith a storage device 113. This storage device 113 may also be a set ofbuffers or registers, a random access memory device, a fixed disk orsimilar storage medium. For example, in one embodiment, the storagedevices associated with initiator component 101 and target component 111may be buffers dedicated to communication over the communication mediumfor each device attached to the medium such as a buffer for a fixed diskor system memory device managed by the target component and a buffer ina chipset managed by a initiator component.

In one embodiment, the initiator component 101 may include a set ofsubcomponents that manage data flow over the communication medium. Thesubcomponents may include a delay module 107, signaling module 109 andcontrol module 105. In one embodiment, the signaling module 109 may be alatch or similar circuit or structure. The signaling module 109 may be atoggle flip flop or equivalent component. The signaling module 109 maytoggle the output on a request line 127 whenever data is available instorage device 103 to be transmitted to the target component 111. Thesignaling module 109 may only be enabled when data is available in thestorage device 103. Enabling or disabling the signaling module 109 bythe device associated with the initiator component 101 via the storagedevice 103 throttles the communication from the initiator component 101end of the interface. The signaling module 109 may toggle the requestline or similarly signal to indicate available data to write or signalthat data may be received from the target component 111. The interfacemay utilize a non return to zero signaling protocol, which is quick andefficient in communicating between the initiator and target components.

In one embodiment, the initiator component 101 may include a delaymodule 107. Delay module 107 receives acknowledgment signals from atarget component 111. In one embodiment, the delay device 107 may delaythe propagation of the incoming acknowledgment signal and divide thesignal into two separate outputs. The first output (t₀) may be a delayedpropagation of the acknowledgement signal based on the time required toallow the acknowledgment line signal to settle into a new state therebyaccounting for skew and distortion on the acknowledgment line as well asthe data lines in the communication medium. The second signal (t₁)further delays the propagation of the acknowledged signal based on themanufacturing characteristics of the initiated component. The differencein time between t₀ and t₁ equates to a minimum pulse width necessary tostrobe the storage device 103 based on the manufacturing characteristicsof the storage device 103 and associated device. The t₀ and t₁ signalsmay be both propagated to the control module 105. The t₁ signal may alsobe propagated to the signaling module 109. For example, the initiatorcomponent 101 may be a part of a central processing unit with a 0.19micron construction. The time difference between t₀ and t₁ maycorrespond to the minimum time necessary to initiate a read operation tothe storage device 103.

In one embodiment, the initiator component 101 includes control module105. The control module 105 manages the signaling to the storage device103 to initiate a read operation for the storage device 103 therebyinitiating a send of the data over the communication medium. The controlmodule 105 receives the t₀ and t₁ signals as inputs from the delaymodule 107. The control module 105 functions as a logical ‘exclusiveOR’. In one embodiment, the control module 105 may be implemented as aset of logical gates defining an exclusive OR operation. The controlmodule 105 generates an output signal that strobes the storage device103 to initiate a read of the storage device to present the data to becommunicated over the communication medium such as a data bus 125. Inone embodiment, the control module 105 may initiate a read after anacknowledgement signal has been received over acknowledgment line 129and after a delay corresponding with the signal t₀. The incomingacknowledgment signal may indicate the readiness of the target component111 to receive data from the initiator component 101. The control module105 may cease to provide this read signal when the t₁ signal isreceived.

In one embodiment, the target component also includes a signaling module117, delay module 119 and control module 115. These components mirrorthe function of the subcomponents in the initiator component 101. Thedelay module 119 may receive request signals from the initiatorcomponent 101. The delay module 119 may generate a first delayed signal(t₀) and a second delayed signal (t₁). The first signal, to, may have adelay corresponding to the skew and distortion associated with therequest line 127. The t₀ signal may propagate to control module 115 thatoperates as a logical exclusive OR. The control module 115 may beimplemented as a set of logical gates that function as an exclusive ORor a similar module capable of signaling to storage device 113 to writethe incoming data on the communication medium 125 into the storagedevice 113. The t₁ signal may be propagated after a further delaycorresponding to the manufacturing characteristics of the targetcomponent 111. The t₁ signal may be propagated to the control module 115to end the signaling of a write to the storage device 113. The t₁ signalmay also be propagated to signaling module 117.

In one embodiment, the signaling module 117 may be enabled for purposesof write operations provided storage device 113 is not full. Whenstorage device 113 is not full and the t₁ signal is received, anacknowledgement signal may toggle acknowledgment line 129. The signalingmodule 117 may be implemented as a latch such as a toggle flip flop orcircuit with similar functionality. The toggle of the signal to theinitiator component 101 using the non return to zero protocol indicatesthat further data may be sent via a write operation to target component111 to be written to storage device 113.

FIG. 2A is a flow chart of the operation of an initiator componentduring a write operation. In one embodiment, the availability of data tobe written in a storage device associated with the initiator componentstarts the write operation process. During the write operation, data inthe storage device associated with the initiator component is to be sentto the target component and stored in the storage device associated withthe target component. In one embodiment, the availability of data may bedetermined by a ‘not empty’ indicator signal generated by the storagedevice associated with the initiator component. This signal may bepropagated to the signaling module to enable the signaling of a requestto a target component.

In one embodiment, the generation of a request signal may be a toggle ofthe signal on the request line using a non return to zero protocol andthe data to be sent may be simultaneously presented on the communicationmedium such as a data bus (block 203). The initiator component maycontinue to present the data on the database that is to be written tothe target component until an acknowledgement signal is received (block205). The incoming acknowledgement signal may be delayed by a delaymodule before being propagated to the signaling module and controlmodule (block 207). The incoming acknowledgment signal may be dividedinto two signals each with a separate period of delay. Both signals maybe propagated to the control module. The first signal starts a read ofthe storage device and the second signal ends the read. The secondsignal may have a delay that differs from the first by the time periodnecessary to successfully signal the storage component to initiate aread and present the next data to be transmitted over the data bus. Thesecond signal may also be propagated to the signaling component. In oneembodiment, a check may be made to determine that further data isavailable in the storage device of the initiator component to transmitto the target component (block 209). If no data is available, then theinitiator component will wait until further data is available. If datais available, then the next data to be sent is retrieved and presentedon the communication medium (block 211). This process may continue bytoggling the signal on the request line and presenting data over thecommunication medium (block 203).

FIG. 2B is a flow chart of one embodiment of the process for the writeoperation at the target component. In one embodiment, the communicationprocess at the target component during a write operation may begin byreceiving a toggled signal on the request line (block 251). Thisincoming signal indicates that the initiator component may be sendingdata over the connecting medium. However, this incoming request signalmay be delayed in its processing by a delay module (block 253). Theincoming request signal may be delayed to accommodate skew anddistortion on the request and data lines and the signal may be split.The first signal may have a first delay corresponding to a required timeof delay to accommodate skew and distortion on the request line. Thesecond signal may be further delayed over the first signal to accountfor the delay needed to accommodate for the manufacturingcharacteristics of the target component. The delayed first signal may bepropagated to the control module to initiate the writing of incomingdata to the storage device associated with the target component (block255). This write period is ended by the generation of the second delayedsignal. The difference in the times of delay may correspond to theminimum pulse width needed to initiate a write for the storage componentassociated with the target component. The second delayed signal may alsobe propagated to a signaling module that toggles a signal on theacknowledgment line. This change in the acknowledgment line signalindicates to the initiator component that further data may be sent.

In one embodiment, this acknowledgement signal may only be generated,however, after a check of the storage device associated with the targetcomponent (block 257). If the storage device is full, then the signalingmodule stalls until the storage device has room to receive further data.If the storage device is not full, then the signaling module may togglethe signal on the acknowledgment line indicating to the initiatorcomponent that further data may be sent (block 259). The targetcomponent may then await a further request signal and data (block 251).

FIG. 3 is a timing diagram showing an example set of signals between aninitiator component and target component during a write operation. Inthe example embodiment, the initiator component 301 may send data to thetarget component 303 to be written to the storage device associated withthe target component 303. The process may begin by the initiatorcomponent 301 toggling the signal on the request line 307 employing anon return to zero signaling protocol. This may begin a first requestphase 317 of the write process. This request signal may be received atthe target component 303 after a skew and distortion of the line issettled 311. The data to be written may be presented on the data lines309 at the beginning of the request phase 317. This write data may alsobe received at the target component 303 on the data lines 313 after theskew and distortion has been settled. In response, the target component303 writes the data to the associated storage device and if that storagedevice has the capacity to receive further data then an acknowledgmentsignal is toggled on acknowledgement line 315 thereby beginning theacknowledgment phase 319.

In the example, the acknowledgment signal may be received by theinitiator component 301 on acknowledgement line 305 after a period ofskew and distortion has settled. In response, if further data isavailable to be written to the target component 303, the initiatorcomponent 301 may again toggle the request line signal 307 starting asecond request phase 321. The next block of data to be written to thestorage device associated with target component 303 may been presentedon the outgoing data lines 309. The request signal and incoming data onthe incoming request line 311 and incoming data lines 313 of the targetcomponent 303 may be received after skew and distortion on the lines hassettled and device manufacturing characteristics accounted for. Thetarget component 303 may then generates an acknowledgement signal iffurther data can be received by the storage device associated with thetarget component 303, hereby initiating the next acknowledgment phase323 by toggling the acknowledgement line 315.

This process may continue until all of the data available in the storagedevice associated with the initiator component 301 has been successfullysent to the target component 303 and stored in the storage deviceassociated with the target component 303.

FIG. 4 is a diagram of one embodiment of the interface in the context ofa read operation. During a read operation, the data requested by aninitiator component 401 may be sent from the target component 411. Theoperation of the initiator component 401 and the target component 411during the read operation may be similar to the behavior of thecomponents during the write operation. However, the initiator component401 may still be responsible for starting the process. Initiatorcomponent 401 may have a storage device 403 that generates a signal thatenables the signaling module 409, so long as the storage device is notfull. The initiator component may also include a delay module 407 thatreceives the acknowledgment signal from the target component 411 anddelays propagation of the acknowledgment signal to account for skew anddistortion on the acknowledgment line 429 before triggering a write ofthe incoming data through control module 409. The delay module 407 mayalso divide the acknowledgment signal and further delay the secondsignal based on the manufacture characteristics of the initiatedcomponent to produce a minimum pulse width for the write signal and togenerate the next request signal via the signaling module 409 if storagedevice 403 is not full.

In one embodiment, the target component 411 may include a storage device413 that enables the signaling module 417 so long as the storage deviceassociated with the target component is not empty. The target component411 may include a delay module 419 that propagates a first delayedsignal based on an incoming request signal. This first delayed signalmay be propagated to the control module 415 that starts the readoperation for the storage device 413 and transmits the data over thecommunication medium such as data bus 425. This read operation is endedby a second delay signal that is generated after the first signal. Thedifference in delay time may be based on a manufacture of the targetcomponent 411 to produce a minimum pulse width necessary for the targetcomponent 411 to conduct a read operation. In one embodiment, the seconddelay signal may be propagated to the signaling module 417, whichgenerates an acknowledgment signal that accompanies the transmission ofdata over the communication medium such as data bus 425.

FIG. 5A is a flowchart of one embodiment of the process for a readoperation in an initiator component. In one embodiment, the readoperation may check an associated storage device to determine ifsufficient space is available in the storage device to receive incomingdata (block 501). If sufficient space does not exist, then the initiatorcomponent may not enable the start of the read processing untilsufficient space becomes available. If sufficient space is available,then a signaling module in the initiator component may toggle a signalon the request line indicating to the target component that theinitiator component is ready to receive data (block 503). The initiatorcomponent then awaits the reception of an acknowledgment signal andaccompanying request data (block 505).

In one embodiment, an acknowledgement signal may be received at thedelayed module in the initiator component. The delay module may delayprocessing of the acknowledgment signal until the skew and distortionare settled on the acknowledgment and data lines. The acknowledgmentsignal may be propagated to the storage device via the control module tostart the write of incoming data to the storage device (block 509). Afurther delayed signal where the further delay may be based on themanufacture type of the initiator component ends the signaling of awrite of the incoming data via the control module. The read process maycontinue to request data or may stall the process if the check of thestorage device indicates that the storage device is full therebymaintaining control of the speed of the communication (block 501).

FIG. 5B is a diagram of one embodiment of the process for receiving andprocessing a read request at the target component. In one embodiment,the process for handling a read operation at the target component beginsby receiving a request signal on the incoming request line (block 551).This request signal may be a toggle of the signal on the request line bythe initiator component. This incoming request signal may be received bythe delay module. The delay module may delay the propagation of thissignal to the rest of the target component (block 553). The receivedsignal may be divided into two signals. The first signal may be delayedfor a time period corresponding to that necessary to settle skew anddistortion of the incoming signal. This first signal is then propagatedto the control module that initiates the read of the storage deviceassociated with the target component and places the requested data on acommunication medium. The second delay signal is propagated after afurther delay corresponding to the minimum delay time necessary toproduce a signal via the control module that is capable of properlyinitiating a read of the storage device. The second delayed signal alsopropagates to the signaling module. A check may be made to determine ifthe storage device contains data, that is, it has data to send to theinitiator component (block 555). If the storage device is empty then thetarget component stalls until data is available. If the storage deviceis not empty, then the data may be sent over the communication mediumand the acknowledge signal may be sent to the initiator componentindicating that further requests may be made (block 557). This processmay continue when the next request signal is received (block 551).

FIG. 6 is a timing diagram of one embodiment of an example readoperation between an initiator component and target component. Thetiming diagram shows that the initiator component 601 may start the readoperation by toggling a request line 607. The request may be received atthe target component 602 on incoming request line 609 after a period ofskew and distortion. The sending of the request signal may start therequest phase 615. Upon receiving the request signal of the targetcomponent 602 and after a defined delay if the target component has datato return an acknowledgment signal may be toggled on acknowledgment line611 and the data requested may be presented on the data lines 613 of thecommunication medium. Sending of the acknowledgement signal andpresentation of the data on the data lines starts an acknowledgementphase 617.

In one embodiment, the acknowledgment signal may be received at theinitiator component on incoming acknowledgement line 603 after a periodof skew and distortion settle. The read data is also received at thesame time on the incoming data lines 605. After a delay corresponding tothe skew and distortion period and manufacturing technology of theinitiator component, a request signal may be sent over the request line607 indicating further read data may be sent. Further requests may begenerated if the initiator component has sufficient space to storeincoming data. A generation of the second request signal starts thesecond request phase 619. The target component receives the incomingrequest signal on request line 609 and in response generates anacknowledging signal and presents the next data block on data lines 613in a new acknowledgement phase 621, if there is data available in astorage device for the target component.

FIG. 7 is a timing diagram and example where a write operation and readoperation are performed simultaneously. The read and write operationsare initiated by the toggling of the request signal on the request line707 by the initiator component 701 starting a first request phase 719.This request signal may be received at the target component 702 on theincoming request line 711. The request signal may be accompanied withdata to be written to the target component 702 on data lines 709. Thewrite data may be received on incoming data lines 713 at the targetcomponent 702 at the time the request signal is received at the targetcomponent 702. This data may be written to the storage device associatedwith target 703. Target component 702, if capable of receiving more dataand it has data to be sent, responds by toggling an acknowledgmentsignal on the outgoing acknowledgment line 715 starting anacknowledgment phase 721. This acknowledgement signal may be sent at thesame time that read data is presented on the outgoing data lines 717.

In the example, the acknowledgment signal may be received at theinitiator component along with the read data on the data lines 705. Inresponse, if the initiator component 701 has sufficient space to receivefurther data and further data to send, a request signal on outgoingrequest line 707 may be toggled and the next write data block may bepresented on the outgoing data bus 709. This starts the next requestphase 723. This process may continue indefinitely into the nextacknowledge phase 725 and beyond.

FIG. 8A is a diagram of one embodiment of the system where the initiatorcomponent and target component operate in different clock domains andare synchronous components. Initiator component 801 in this embodimentcontains a storage device 803, control module 805, combined delay andsignaling module 807 and a synchronization module 809. The targetcomponent 811 also contains a storage device 813, control module 815,combined delay and signal module 817 and synchronization module 819. Theinitiator component and target components and subcomponents operate in afashion similar to those in asynchronous embodiment. The initiatorcomponent and target component both contain synchronization modules 809and 819 that synchronize an incoming signal such as a signal on therequest line or acknowledgment line with the clock domain of thecomponent. A separate delay component may not be utilized because theinitiator component and target component are synchronous devices insteadof asynchronous devices. The storage devices 803 and 813 throttle thecombined signal and delay modules 807 and 817 when the storage device803 on the initiator side during a read operation is empty or when thestorage device on the target side is full during a write operation.

FIG. 8B is a diagram of one embodiment of a synchronous initiator andtarget component interface capable of performing a read operation. Thesame subcomponents may be present in the initiator component 801 andtarget component 811 as were present in the synchronous write operationembodiment. The throttling of the combined signal and delay modules 807and 817 are reversed so that the initiator component 801 disables thesignaling module when its storage device is full and not able to receivedata from the target component 811 and the target 811 disables thesignaling module 817 when it is empty and has no data to send to theinitiator component 801.

FIG. 9A and FIG. 9B show an embodiment of the initiator and targetinterface including a sequence generator and correlator to train thepair to communicate at a desired bit error rate. The previousembodiment, relied on known skew and distortion characteristics as wellas manufacturing characteristics of the components to determine thenecessary delay in handling signals. This embodiment of the initiatorand target component interface may be utilized when the characteristicsof the data link, acknowledgment lines and request lines are unknownbetween the initiator component 901 and target component 911. Thisembodiment may also be used in scenarios where it is desired that aspecific bit error rate be maintained over time.

FIG. 9A is a diagram of an embodiment where the delay of the targetcomponent is trained. In one embodiment, the initiator component 901 andtarget component 911 may contain a sequence generator 903 and correlator913, respectively. Sequence generator 903 may be coupled to thecommunication medium such as data bus 925 in parallel with a storagedevice or a similar component that communicates over the communicationmedium. The initiator component 901 also contains a delay module 907 andcontrol module 905. These modules do not replace the modules in thesynchronous and asynchronous embodiments discussed above, but rather areutilized during an initialization period or on a periodic basis to trainthe initiator component 901 based on the operating characteristics ofthe communication medium between the initiator component 901 and targetcomponent 911 and to maintain a specified error bit rate. The targetcomponent 911 may include a correlator 913 that is also coupled to thecommunication medium such as data bus 925. The target component 911 mayalso include the control module 915 and delay module 917. Again, thesecomponents do not replace the components discussed in regard to thesynchronous or asynchronous embodiments, but rather are utilized duringan initialization period or on a periodic basis to determine the currentcharacteristics of the communication medium to maintain a specifiederror bit rate.

The sequence generator 903 may continuously send a training sequencethat may be any number of data block over the communication medium tothe target device. Initiator component 901 may simultaneously send arequest signal with the training sequence. The target component 911 mayreceive a training sequence at the correlator 913 and may compare theincoming sequence with a known training sequence to determine the errorrate in the incoming training sequence. The incoming request signals maybe delayed by the delay module 917 to attempt to accommodate the skewand distortion on the line before passing the incoming signal over tothe control module 915 that enables the comparison of the incomingsignal with the known training sequence. If the comparison results in anerror rate that is greater than desired, then the target component 911may increase the delay in delay module 917 iteratively until the desiredbit error rate is obtained.

FIG. 9B is a diagram of an embodiment for training the delay in theinitiator component. In one embodiment, the initiator component 901 mayreceive the training sequence from the target component 911 at acorrelator module 913 situated in the initiator component 901 andconnected to the communication medium. The sequence generator 909 in thetarget component 911 may continuously transmit the training sequenceuntil the initiator component 901 is able to tune the delay module 907to account for a proper skew and distortion time period and to attainthe desired bit error rate.

FIG. 10 is a diagram of one embodiment of a computer system utilizing aninitiator-target component interface to manage communication betweensystem components. In one embodiment, the computer system may include acentral processing unit (CPU) 1001, communication hub 1009, memorydevice 1011, graphics processor 1007, 10 hub 1121, set of peripherals1125 and similar components. The CPU 1001 may be in communication withthe communication hub via a bus. The CPU 1001 may control thecommunication with the communication hub 1009 with an initiatorcomponent 1003 that communicates over the bus with a target component1113. Similarly, the communication hub 1009 may communicate with amemory device 1111 through an initiator component 1115 that communicatesover a memory bus with target component 1131.

In one embodiment, the communication hub may have a bi-directionalinterface configuration to control communication over the memory buswith a memory 1111. The type of traffic may be divided between theinitiator and target component pairs of the bi-direction or splitinterface. For example, in one embodiment, the communication hub 1009may be in control of the write operations while the memory device 1011may be in command of the execution of read operations by having aninitiator component 1129. Data communication may be divided between anynumber of initiator and target component pairs to control communicationover a bus or set of buses between any system components that supportthe initiator-target component interface.

In one embodiment, the computer system may have a many to one or one tomany relationship between the initiator components and targetcomponents. For example, in one embodiment, the IO HUB 1121 may have aninitiator component 1123 that is responsible for coordinatingcommunication with a set of peripherals 1125 each having a targetcomponent 1127.

FIG. 11 is a diagram of one embodiment of the use of the initiatorcomponent and target component interface to control communication overother types of communication media such as common networkingcommunication media between network devices. In one embodiment, theinitiator component and target component interface may be utilized tocontrol communication over a communication medium such as optical orcoaxial cable, radio frequency communication, satellite links or similarcommunication medium. This interface may be utilized to managecommunication between network devices 1101, 1103, computers, handhelddevices, console device and similar types of electronic devices. Theinterface may be utilized over any distance and at any scale. Thisinterface may be used within an integrated circuit between circuits overprinted circuit boards between network devices, over coaxial cable,optical lines, and similar communication medium. For example, devicesmay utilize a set of initiator component and target component pairs suchas pairs 1105, 1109, 1107 and 1111 in the example network devices tomanage traffic flow between device of any generation or speed.

The initiator-target component interface may be implemented in software,for example, in a simulator, emulator or similar software. A softwareimplementation may include a microcode implementation. A softwareimplementation may be stored on a machine readable medium. A “machinereadable” medium may include any medium that can store or transferinformation. Examples of a machine readable medium include a ROM, afloppy diskette, a CD-ROM, an optical disk, a hard disk, a radiofrequency (RF) link, and similar media and mediums.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes can be made thereto withoutdeparting from the broader spirit and scope of the invention as setforth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense.

What is claimed is:
 1. A method, comprising: generating a request signalon a first line; sending data over a communication medium in response tothe request signal; and generating an acknowledge signal on a secondline to throttle a transfer of data in response to a first delayedversion of the acknowledgment signal received from a target.